UNIVERSITY OF ILLINOIS BULLETIN 

Issued Weekly 

Vol. XIV MAY 28, 1917 No. 39 

lEntered as second-class matter Deo. 11, 1912, at the Post Office at Urbana, Ill., under the Act of Aug. 24, 1912.1 


EFFECTS OF STORAGE UPON THE 
PROPERTIES OF COAL 


BY 


S. W. PARR 



BULLETIN No, 97 

ENGINEERING EXPERIMENT STATION 

PUBLISUED BY THE UNIVERSITY OF ILLINOIS, UrBANA 


Price : Twenty Cents 
European Agent 
Chapman & H.all, Ltd., London 












T he Engineering Experiment Station was established by act of 
the Board of Trustees, December 8, 1903. It is the purpose 
of the Station to carry on investigations along various lines of 
engineering and to study problems of importance to professional engi¬ 
neers and to the manufacturing, railway, mining, constructional, and 
industrial interests of the State. 

The control of the Engineering Experiment Station is vested in the 
heads of the several departments of the College of Engineering. These 
constitute the Station Staff and, with the Director, determine the 
character of the investigations to be undertaken. The work is carried 
on under the supervision of the Staff, sometimes by research fellows 
as graduate work, sometimes by members of the instructional staff 
of the College of Engineering, but more frequently by investigators 
belonging to the Station corps. 

The results of these investigations are published in the form of 
bulletins which record mostly the experiments of the Station’s own staff 
of investigators. There will also be issued from time to time, in the 
form of circulars, compilations giving the results of the experiments of 
engineers, industrial works, technical institutions, and governmental 
testing departments. 

The volume and number at the top of the title page of the cover 
are merely arbitrary numbers and refer to the general publications of 
the University of Illinois: either above the title or below the seal is given 
the number of the Engineering Experiment Station bulletin or circular 
which should be used in referring to these publications. 

For copies of bulletins, circulars, or other information address the 

Engineering Experiment Station, 
Urbana, Illinois. 


UNIVERSITY OF ILLINOIS 
ENGINEERING EXPERIMENT STATION 

Bulletin No. 97 May, 1917 


EFFECTS OF STORAGE UPON THE 
PROPERTIES OF COAL 


BY 

S. W. PARR 

'( 

Professor of Applied Chemistry 


) > 

> ) 


ENGINEERING EXPERIMENT STATION 

Published bt the University op Illinois, Urbana 


• > > 







CONTENTS 


1 \\%n 

yzs 


PAGE 

I. Introduction.5 

II. Summary of Results.6 


III. Effects of Storage Upon Coal.8 

HEATING AND SPONTANEOUS COMBUSTION 

1. Oxidation of Pyrites.9 

2. Growth of Sulphates.10 

3. Effect of Fineness of Division.11 


4. Effect of Moisture.12 

5. Summary on Oxidation.14 

' I 

DETERIORATION 

6. Indicated Heat Losses.22 

7. Escape of Combustible Gases.23 

8. Absorption of Oxygen.23 

9. Increase in Weight.24 

10. Decrease of Ash Percentages.25 

IV. Moisture Values for Weathered Coal .27 

V. Summary of Chemical Studies .28 

VI. Changes in Physical Properties.30 

1. Sizing Test.30 

VII. Boiler Tests on Weathered Coal .36 

VIII. Conclusions .38 


0* Of D. 

NOV ID tsi; 




















LIST OF TABLES 


NO. 


PAGE 


1 . 

2 . 

3. 

4. 

5. 

6 . 

7. 

8 . 
9. 

10 . 

11 . 


I O 


13. 

14. 

15. 

16. 
17. 


Growth of Sulphate: Comparison between Fine and Coarse Laboratory 
Samples.11 

Sulphate Sulphur as Found in Various Sizes of Coal.11 

Effect of Low Moisture on the Formation of Suljihate.12 

Sulphate in Laboratory Samples, Showing Conditions Attending Presence 


of Moisture and Sulphur.13 

Vermilion County Nut Coal.15 

Williamson County Nut Coal.16 

Sangamon County Nut Coal.19 

Vermilion County Screenings.20 

Williamson County Screenings.21 

Sangamon County Screenings.22 


Indicated Ash at the Beginning and at the End of Six Years in Stor¬ 
age in Open Bins.25 

Increases in Weight of Coal During Storage, in Eelation to the Indicated 
Decrease in Heat Value.26 


Percentage of Moisture in Weathered Coal, Loss Due to Air-Drying, 

and the Amount Eetained by the Air-Dried Samples.30 

Eesults of Sizing Tests on Nut Coal Stored in Open Bins.31 

Eesults of Sizing Tests on Screenings in Open Bins.32 

Increase in Pine Material After One and One-Half and Six Years . . 35 

Eesults of Boiler Tests with Mission Field Fresh Coal and with Weathered 
Coal After Six Years in Storage.37 


LIST OF FIGUEES 


NO. PAGE 

1. Open Storage Bins.17 

2. Covered Storage Bins.17 

3. Eevolving Screens Used in Sizing Tests (Univ. of Ill. Eng. Sta. Bui. 78, 

1909). 33 


3 




















EFFECTS OF STORAGE UPON THE PROPERTIES OF COAL 


I. Intkoduction 

The need of a thorough understanding of the conditions affecting 
the storage of bituminous coal is becoming more and more apparent. 
The demand for coal at certain seasons is so gre4t that both mining 
and transportation facilities are taxed severely in meeting it. Provi¬ 
sion has not been made for adequate and proper storage of bituminous 
coal either at the mines or at the distributing centers, and as a result 
of this lack there must be maintained throughout the year a sufficient 
number of operating mines to meet what may be termed the ‘‘peak 
load” which occurs during the winter months. At such times also 
there is often a shortage of cars, although a smaller number of cars 
even than is now available would be needed if the work of transporta¬ 
tion could be more evenly distributed throughout the year. Mr. C. G. 
Hall, Secretary of the International Railway Fuel Association, has 
made an estimate showing that the number of excess mines over and 
above those which would be normally required to meet the demand, 
provided their work could be distributed evenly through the year, 
represents an investment in the United States of $450,000,000. In 
addition, the extra coal cars, which must be at hand when the demand 
is heavy but which stand idle accumulating rust for the rest of the 
year, have cost the railways no less than $105,000,000 more than would 
be necessary if the same tonnage could be hauled at an even rate. 
These wastes eventually affect the cost per ton of coal, which every 
one must pay as a contribution toward the capital investments. 

The difficulties attending these conditions are accentuated by 
occasional abnormal demands such as are created upon the approach 
of any date for readjusting the wage scale with the accompanying 
pos.sibility of a strike or lockout. For example, in addition to the 
normal excess demand during the winter months of 1915-16, a com¬ 
pilation of the published amounts of coal being stored by the various 
railway systems and larger users only, in view of a p'ossible strike in 
April, aggregated over 3,000,000 tons. 

The industrial disturbances do not include all of the serious con¬ 
siderations, however. If we con.sider the labor distresses that are 



6 


ILLINOIS ENGINEERING EXPERIMENT STATION 


accentuated as a result of irregular employment, it at once appears 
that the problems involved are of great sociological as well as of eco¬ 
nomic interest. 

The work here recorded is a continuation of certain studies, the 
results of which have been published in bulletin form by the Engineer¬ 
ing Experiment Station under the titles of ‘‘The Weathering of 
Coal,”* “The Occluded Gases in Coal,”t and “The Spontaneous 
Combustion of Coal. 

The subjects treated in these publications are of fundamental im¬ 
portance, and a thorough understanding of the principles involved 
under each subject is necessary before any adequate discussion can 
be undertaken of the problems connected with the storage of coal. 
The investigations described in Bulletin 38 of the University of Illi¬ 
nois Engineering Experiment Station, on “The AYeathering of Coal” 
were conducted with car-lot samples of coal stored under various con¬ 
ditions. The data obtained covered a period of one year. The investi¬ 
gation was continued for an additional period of five years more, or 
for a total period of six years. The coal was then turned over to the 
power plant for steam generation, and boiler tests were made to estab¬ 
lish the character of the various samples. These data, together with 
other facts bearing upon the general subject of coal storage, have 
accumulated to an extent which warrants their being brought together 
for record and discussion in this form. 

Special acknowledgment is due Mr. J. M. Lindgren, Chemist, and 
Mr. F. II. AVhittum, Assistant Chemist, for the analytical data accu¬ 
mulated beyond the first-year period. Their experience and skill 
in the matter of sampling and in the use of analytical and calori¬ 
metric methods have been especially noteworthy. 

II. Summary of Results 

The facts established by this investigation may be briefiy sum¬ 
marized as follows: 

(1) Freshly mined coal is chemically very active. Certain 
constituents have a marked affinity for oxygen, with which they 
enter into combination at ordinary temperatures. AA^hile the 
extent of this reaction depends upon the variety of the coal and 


*S. W. Parr and W. F. Wheeler, Univ. of Ill. Eng. Exp. Sta. Bui. 38, 1909. 
tS. W. Parr and Perry Barker, Univ. of Ill. Eng. Exp. Sta. Bui. 32, 1909. 
$S. W. Parr and F. W. Kressman, Univ. of Ill. Eng. Exp. Sta. Bui. 40, 1910. 



EFFECTS OF STORAGE UPON THE PROPERTIES OP COAL 


7 


the amount of these active constituents, a very important factor 
is the fineness of division or the sum total of the superficial 
areas of the particles, and accessibility of oxygen to the mass. 

(2) The actual loss of heat value resulting from storage 
is small. It is evident that upon mining out the coal from the 
bed certain volatile constituents of the marsh gas variety are set 
free. The heat values represented by such exudations are not 
great. The tendency to absorb oxygen from the air is also a 
marked characteristic of freshly mined coal. This is in reality 
a chemical process, and is accompanied by the generation of a 
small amount of heat, but these heat losses, compared with the 
total heat available in the coal, are insignificant. Indeed, it may 
be fairly questioned whether the heat losses are not more ap¬ 
parent than real since there is an increase of weight due to the 
absorption of oxygen. Such increase will in itself lower to a 
corresponding degree the indicated heat value per pound of coal. 

(3) There is an increase of “fines’’ or slack resulting from 
storage, greater with some coals than with others. This, together 
with the saturation of the free burning constituent with oxygen, 
slows up the fire and gives the appearance of being lacking in 
heat value. However, with an increase of draft and a correct 
understanding of the combustion conditions to be maintained, a 
most excellent over-all efficiency can be secured even from coals 
which have been in storage for long periods. 

(4) Bituminous coal can be stocked without appreciable 
loss ’of heat values provided the temperature is not allowed to 
rise above 180 degrees F. Any method of storage, to be success¬ 
ful, must either check or prevent the absorption of oxygen to 
.such an extent that the generation of heat shall not proceed 
faster than the dissipation and loss of heat due to absorption or 
radiation. 

(5) Underwater storage prevents loss of heat values, and 
is not accompanied by deterioration in physical properties, such 
as slacking. The water retained by the coal upon removal is 
substantially only that held by adhesion or capillarity. 

(6) Dry storage is safer and more satisfactory if the fine 
material is screened out at the storage yard and lump only, pref¬ 
erably sized, is stocked. 


8 ILLINOIS ENGINEERING EXPERIMENT STATION 

It will be seen from this summary that the most serious part of 
the problem relates to the matter of spontaneous heating, and prob¬ 
ably the least serious phase relates to deterioration and actual loss 
of heat values. It is certain that at the present time a better under¬ 
standing of these difficulties has been reached, and there is reason for 
. believing that this better understanding of the fundamental principles 
involved will lead to some practicable and safe procedure for the 
stocking of bituminous coal. 

III. Effects of Storage Upon Coal 

HEATING AND SPONTANEOUS COMBUSTION 

It is a well established fact that freshly mined coal has a large 
absorptive capacity for oxygen. In Bulletin 32, ‘ ‘ The Occluded Gases 
in Coal,” it is made evident that this avidity for oxygen is most 
marked in the freshly mined coal, and after exposure to the air for 
four or five months an approach to the saturation point seems to be 
reached after which very little oxygen is taken on. A correct inter¬ 
pretation of this phenomenon is essential to an understanding of the 
spontaneous heating of coal piles. The natural conclusion would be to 
the effect that the oxygen has been simply absorbed or occluded; that 
it was a physical rather than a chemical change. The evidence, how¬ 
ever, of all the more recent investigations goes to show that it is in fact 
a chemical combination and that it is accompanied by the generation 
of a small amount of heat. In Bulletin 46, ^‘The Spontaneous Com¬ 
bustion of Coal,”* it is seen that at a temperature of from 35 to 40 
degrees C (95 to 104 degrees F), and with free access of air, the 
amount of heat generated caused a rise in temperature of from 1 to 
11/4 degrees C per day. Porter and Ovitzf have measured the quantity 
of oxygen taken up by a sample of Franklin County coal and found 
it to be approximately 0.8 per cent of the weight of the coal. More¬ 
over, there is only a very small amount of CO 2 formed. This is ex¬ 
plained by the fact that the presence of certain unsaturated com¬ 
pounds allows the oxygen to enter the molecular structure of the coal, 
with which compounds the oxygen readily combines. 

These references are a few of many that might be brought for¬ 
ward showing that at ordinary temperatures freshly mined coal unites 


♦Parr and Kressman, Univ. of Ill. Eng. Exp. Station Bui. 46, 1910. 
tJournal Industrial and Engineering Chemistry, Vol. 2. 



EFFECTS OF STORAGE UPON TTIE PROPERTIES OF COAL 


9 


chemically with oxygen and that in the process there is generated a 
certain amount of heat. 

1. Oxidation of Pyrites .—Much consideration has been given by 
various investigators to the role of iron pyrites in promoting the heat¬ 
ing of coal. In the experiments carried out by Dennstedt and Bunz 
in 1908,* it appears that self-ignition may be brought about in the 
case of coals having only small amounts of pyritic sulphur. The con¬ 
clusion is made, therefore, that the presence of iron pyrites is not an 
essential condition for spontaneous heating. Other investigators work¬ 
ing along similar lines have reached the same conclusion. Still others 
seem to have evidence that pyritic sulphur is an active element in the 
case. A summary of opinions on this point is given as follows:! 

‘‘As to what part sulphur compounds, especially pyrite, play in 
the spontaneous ignition of coal, opinions differ greatly. Some believe 
pyrite to be the leading factor, while others believe it plays no part 
at all, or, if so, ascribe to it a position of minor importance and believe 
its action to be merely a subsidiary one. The oxidizing action of the 
air upon pyrite is, however, admitted, and the notion seems to be 
fairly general and well established that pyritic oxidation tends to 
raise the temperature of the coal. On the other hand, it is seen from 
the work of Fayol, Dennstedt and Bunz, Threlfall and others that 
coals containing pyrite in a quantity too insignificant to be noticed are 
very apt to ignite spontaneously. The Newcastle coal of New South 
Wales is also a very good example of this class of coals. Others, how¬ 
ever, believe that the only infiuence of the pyrite is a mechanical one, 
in which the oxidation of the thin films of pyrite in the coal serves 
merely to break up the coal. ’ ’ 

Investigations of this type, having for their object a study of the 
processes of oxidation which occur at normal temperatures, are ex¬ 
tremely important, especially in that phase of the work which seems to 
have fully established the fact of oxidation of the organic constituents 
of the coal. The conclusions are somewhat at fault, however, in assum¬ 
ing that as a consequence the pyritic oxidation is of little importance. 
It is true that a coal may heat seriously even though pyritic sulphur is 
absent. This does not constitute proof, however, that the presence of 

*Zeit fiir Aug. Cliemi., Vol. 21 , pp. 1821-35, 1908. 

tParr and Kressmann, “The Spontaneous Combustion of Coal,” Univ. of Ill. Eng. 
Exp. Sta. Bui. 46, pp. 83, 1910. 



10 


ILLINOIS ENGINEERING EXPERIMENT STATION 


pyritic sulphur in coals may not be equally, or even more largely, 
responsible for heating than the organic constituents. , 

This is clearly set forth in Bulletin 46.* On page 52, under ‘‘Iron 
Pyrites, ’ ’ a summarized statement is given as follows: 

‘ ‘ The presence of sulphur in the form of iron pyrites is a positive 
source of heat due to the reaction between sulphur and oxygen. This 
may be conveniently referred to as the second stage in the process of 
oxidation. Here again rapidity of oxidation is directly dependent 
upon fineness of division. Since coals, as a rule, have a much higher 
earthy or ash content in the fine duff, and since iron pyrites is a large 
component of this material, it follows that the presence of dust or 
duff in all coals of the Illinois type is a positive source of danger. ’ ’ 

However, in this summary the authors give first place in time and 
effect to the oxidation of the organic matter and consider that the 
activity of the pyrites waits somewhat upon the rise in temperature 
from such organic oxidation before action with sulphur reaches a seri¬ 
ous phase. Special emphasis was laid upon the oxidation of sulphur as 
a source of heat, but the experiments did not specifically give direct 
evidence as to the temperature at which pyritic sulphur began to 
oxidize. 

2. Growth of Sulphates .—Data on the oxidation of sulphur have 
recently been developed in connection with the study of variations 
in the determination of ash vainest which have a bearing in this con¬ 
nection. The fact appears that the oxidation of sulphur is active at 
ordinary temperatures provided (a) that the pyritic iron be finely 
divided, and (b) that free moisture be present in sufficient amount to 
satisfy the reactions involved. For example, a certain series of bed 
samples of coal had been ground to 60-mesh and laboratory samples 
taken of about 75 grams which were placed in 4-ounce bottles with rub¬ 
ber stoppers. These samples were retained in the laboratory at room 
temperature from August, 1912, to April, 1913, at which time they 
were analyzed for sulphur in the sulphate or SO 3 form. For com¬ 
parison, the original samples ground only to lO-mesh were similarly 
analyzed. The results are shown in Table 1. 


Tarr and Kressmann, Univ. of Ill. Eng. Exp. Sta. Bui. 40, 1910. 
tS. W. Parr, Ill. State Geo. Survey, Co-Op. Bui. 3, 191,5. 



EFFECTS OF STORAGE UPON THE PROPERTIES OP COAL 


n 


Table 1 

Growth of Sulphate 

Comparison between Fine and Coarse Laboratory Samples 


Lab. No. 

County 

H 2 O 

Total 

Sulphur 

SO 3 

60-Mesh 
Aug., ’12 

SO 3 

60-Mesh 
April, ’13 

SO 3 

lO-Mesh 
April, ’13 

5365 

Mercer. 

6.33 

5.29 

0.95 

1.46 

0 86 

5367 

Grundy. 

8.84 

2.27 

0.39 

0.38 

0 18 

5370 

Mercer. 

4.49 

4.92 

0.47 

0.49 

0 25 

5372 

Mercer. 

4.86 

5.46 

0.63 

1.25 

1 12 

5376 

Grundy. 

7.66 

2.73 

0.61 

1.12 

0.86 

5388 

La Salle. 

7.93 

5.20 

1.42 

1.79 

0 82 

5381 

La Salle. 

8.05 

4.83 

0.62 

1.20 

0.81 


3. Effect of Fineness of Division .—From the results in Table 1 
it is evident that oxidation of sulphur has occurred at ordinary tem¬ 
peratures. Five of the seven samples have had from 30 to 40 per 
cent of the total sulphur thus changed. The second and third sam¬ 
ples in this table show no such oxidation. In the second the content 
of total sulphur is low and of this the actual sulphur in the pyritic 
form is, of course, still lower. Data on this point were not obtained. 
In the third sample the water content is lower than that in the other 
samples of the table. AVhether this affords a valid explanation is 
uncertain. At any rate the point here emphasized is the fact that in 
the majority of the samples oxidation of the pyritic sulphur occurred 
in large amounts and at room temperatures. The next point was to 
determine what conditions were chiefly responsible in this reaction. 
The last column of the table affords some information. Here it is seen 
that with one exception the coarse or 10-mesh material had little or 
no indication of sulphur oxidation. To test further the effect of 
flneness of division, two of these original samples, about two pounds 
each, were sized and the sulphate sulphur determined for each size. 
The results are given in Table 2. 


Table 2 

Sulphate Sulphur as Found in Various Sizes of Coal 


Lab. No. 

10-Mesh 

20-Me8h 

40-Mesh and Over 

5372 

0.91 

0.89 

1.43 

5388 

0.53 

0.60 

1.42 


It is shown by this table that while substantially no increase in 
sulphate occurred up to the 20-mesh size, the increase was very 



































12 


ILLINOIS ENGINEERING EXPERIMENT STATION 


marked in the 40-mesh sample, though it should be said that the 
40-mesh sample contained also all of the finer material passing through 
that sieve. This record further emphasizes the fact that oxidation of 
sulphur increases in activity as the size of particles is decreased and 
the superficial area in any given mass correspondingly increased. 

4. Ejfect of Moisture .—In seeking an explanation for the lack 
of uniformity in behavior due to sizing alone, it was thought that pos¬ 
sibly the amount of free moisture in the sample as well as the per¬ 
centage of FeS 2 might play an important part. A number of samples 
were, therefore, selected in which the free moisture was low. In these 
cases the growth of sulphate in the laboratory sample was small as 
shown in Table 3. 


Table 3 

Effect of Low Moisture on the Formation of Sulphate 
All Values on the Dry Coal Basis 


Lab. 

No. 

Moisture 

Total 

Sulphur 

Sulphate 
(SO 3 ) in 
Lab. 
Sample, 
60-Mesh 
75 Days 
in Sample 
Bottle 

SO 3 in 
3-Lb. 
Gross 
Sample. 
All Sizes 
up to 

M Inch 
after 15 
Days in 
Container 

.3-Lb. 
Gross 
Sample. 
All Sizes 
up to 
Inch 
after 

75 Days 

Sizing of Gross Sample 
after 75 Days 

SO 3 in 
10-Mesh 
Size 

SO 3 in 
20-Mesh 
Size 

SO 3 in 
40-Mesh 
Size 

6399 

6400 

1.74 

2.03 

3.65 

3.19 

.214 

.218 

.200 

.230 

.198 

.228 

.176 

.199 

.164 

.195 

.215 

.257 


As affording further evidence on this general proposition, 28 
samples of coal were selected from the various districts of the state, 
and sulphate determinations made on the laboratory samples ground 
to 60-mesh which had been in storage from the early part of 1912 
until June, 1913. Unfortunately, the sulphate factors for the fresh 
coal are not available, but the table shows that in those samples in 
which both the water and the sulphur contents were high, there 
was a greater increase in the percentage of oxidized sulphur than in 
the case of samples in which water and sulphur contents were low. 
Note especially Nos. 5359-5389, inclusive. Table 4. 

Doubtless, there are other circumstances connected with the oxi¬ 
dation of sulphur which are of interest, such as the presence of 
catalyzers, the source of oxygen for satisfying the conditions of the 

















EFFECTS OF STORAGE UPON THE PROPERTIES OF COAL 


13 


Table 4 

Sulphate in Laboratory Samples, Storage Time from March, 1912, to 
June, 1913, Showing Conditions Attending Presence 
OF Moisture and Sulphur 


Lab. 

No. 

County 

Coal Bed 

HgO 

Total Sulphur 
Dry Coal 

SO3 Dry 
Coal 

Remarks 

4699 

Vermilion. 

6 N 

2.30 

2.44 

0.18 

Sulphate was 

4702 

Vermilion. 

6 N 

2.08 

2.75 

0.15 

determined 

4706 

Vermilion. 

6 N 

2.08 

3.48 

0.32 

June 2, 1913, 

4707 

Vermilion. 

6 N 

1.82 

4.82 

0.35 

0 n pulverized 

4716 

Vermilion. 

7 N 

2.31 

4.06 

0.62 

samples col- 

4724 

V ermilion. 

7 N 

1.95 

3.77 

0.60 

lected Febru- 

4727 

Vermilion. 

7 N 

1.91 

3.33 

0.37 

ary to June, 

4734 

Vermilion. 

7 N 

2.24 

2.59 

0.22 

1912. 

4744 

Vermilion. 

6 N 

4.58 

1.94 

0.29 


4789 

Franklin. 

6 S 

3.88 

0.52 

0.02 


4811 

Franklin. 

6 S 

2.41 

1.53 

0.22 


4994 

Saline. 

5 S 

2.82 

2.32 

0.54 


5006 

Williamson. 

6 S 

3.25 

1.11 

0.12 


5011 

Franklin*.. 

6 S 

4.14 

1.53 

0.18 


5024 

Saline. 

5 S 

5.87 

3.78 

0.80 


5121 

Williamson. 

6 S 

3.73 

1.42 

0.11 


5122 

W illiamson. 

6 S 

6.25 

1.46 

0.12 


5134 

Williamson. 

6 S 

6.25 

1.24 

0.10 


5224 

Franklin. 

6 S 

5.87 

1.12 

0.06 


5339 

Mercer. 

1 N 

3.21 

5.66 

0.98 


5359 

Rock Island. 

1 N 

4.84 

6.56 

2.14 


5361 

Rock Island. 

1 N 

5.74 

4.56 

1.08 


5362 

Rock Island. 

1 N 

4.96 

5.26 

1.15 


5364 

Mercer. 

1 N 

6.34 

4.94 

1.69 


5368 

Grundy. 

2 N 

7.08 

3.04 

0.59 


5369 

Grundy. 

2 N 

6.98 

2.53 

0.44 


5377 

Grundy. 

2 N 

7.83 

4.00 

1.34 


5389 

La Salle. 

2 N 

7.71 

3.57 

0.83 



reaction, the mercasite or pyrite form of the sulphide crystals, the 
method of distribution, whether in microscopic or massive aggregates, 
the character and influence of the associated material, and the segre¬ 
gation of sulphate crystals towards the finer materials. Indeed, the 
more thorough understanding of some of these points might contribute 
in a very practical way to our knowledge of the conditions which pro¬ 
mote the heating of coal. Definite information along these lines 
depends upon further study. However, for purposes of this dis¬ 
cussion it is of importance to note that at least two conditions, if 
existing, namely, fineness of division, and presence of moisture, will 
result in oxidation of the sulphur. Supplementary to this should be 
recalled the fact already developed in Bulletin 46 that the oxidation 
of 0.5 per cent of sulphur, or approximately less than % of the 
amount present in the average Illinois coal, would produce sufficient 
heat to raise the temperature of the mass, not allowing for radiation 
losses, about 125 degrees F. If the initial temperature were 50 
degrees F, an increase to 175 degrees would approach the danger 











































14 


ILLINOIS ENGINEERING EXPERIMENT STATION 


point. At about 180 degrees the activity reaches a stage owing to 
the greater rapidity of oxidation at that temperature, at which the 
chemical reaction quickly proceeds to the point where it becomes 
autogenous.* 

In the discussion concerning the generation of heat from sulphur 
oxidation it is not intended to minimize the effect of oxidation of the 
organic matter as an initial source of heat, independent of the activity 
of the sulphur. In bituminous coals the two, doubtless, proceed inde¬ 
pendently, but where both activities exist together there is an acceler¬ 
ation of the reaction due to the rapid rise of temperature. In this 
manner there is a greater quantity of heat produced in a given 
period of time, and hence the coal mass comes more quickly and more 
positively to the autogenous or danger stage. 

5. Summary on Oxidation .—Oxidation of the organic materials 
in freshly mined coal is active in all coals of the bituminous or lig- 
nitic type. The conditions which accelerate the action are increase 
of temperature and fineness of division. 

Oxidation of the sulphur of iron pyrites is active provided the 
sulphide of iron is finely divided and there is sufficient moisture 
present to satisfy the reaction. The quantity of finely divided pyritic 
material will of course be greater in screenings than in lump, and 
since the ash content in screenings is from one to two times as great 
as in the lump, the quantity of pyritic sulphur is correspondingly 
greater. 

The conditions to be observed in stocking coal so far as oxidation 
is concerned, are thus fairly well outlined. The enumeration of these 
<3onditions will be taken up later. 

DETERIORATION 

Experiments on the weathering of coal are described in Bulletin 
38. t Car lots were stored in open and in covered bins and smaller 
lots of 100 to 200 pounds under water. The samples for determina¬ 
tion of heat values were taken on the day of mining the coal, and 
thereafter at seven days, two months, six months and one year. 

♦Note the abrupt change in the direction of the curves at 80 degrees C, showing 
temperature rise, as in “Spontaneous Combustion of Coal,” Univ, of Ill. Eng, Exp. Sta. 
Bui. 4G, p, 28. 

tParr and Wheeler, “The Weathering of Coal,” Univ. of Ill. Eng. Exp. Sta. Bui. 38, 
1909. * 



EFFECTS OF STORAGE UPON THE PROPERTIES OF COAL 15 

All of the samples with the exception of the submerged samples, 
were continued in storage beyond the period covered by the results 
presented in Bulletin 38, for a total period of six years. Two addi¬ 
tional sets of laboratory samples were taken; one after a total period 
of three years, and another at the end of six years. After the storage 
in the original bins for four years, both the covered and open lots 
were moved to a new location. After a period of six years, final 
laboratory samples were taken in connection with the cleaning up 
of the various lots and the making of boiler tests. Five standard 
boiler tests were made at the close of the period. 

For greater convenience all of the analytical results for the entire 
period are presented in Tables 5 to 10, inclusive. 


Table 5 

Vermilion County Nut Coal 


Sample Taken 

Dry Coal 

B. t. u. 

Referred 
to Actual 
or Unit 
Coal 

after Mining 

Ash 

Sulphur 

B. t. u. 


Lab. No. 


Decrease 


. t. u. 


Per Cent 


STORED IN EXPOSED BINS 


1031 

Same day. 

10.55 

4.25 

12991 

14814 



1081 

7 days. 

13.98 

2.65 

12412 

14716 

98 

0.66 

1240 

2 months. 

14.21 

2.47 

12265 

14577 

237 

1.60 

1656 

6 months. 

13.53 

2.10 

12396 

14575 

239 

1.61 

2088 

1 year. 

13.62 

2.82 

12282 

14498 

316 

2.13 

4105 

3 years. 

13.22 

1.75 

12018 

14075 

739 

4.98 

7298 

6 years. 

13.06 

1.58 

11984 

14000 

814 

5.49 


STORED IN COVERED BINS 


1031 

1081 

1249 

1662 

2094 

4101 

7372 

Same day. 

7 days. 

2 months. 

6 months. 

1 year. 

3 years. 

6 years. 

10.55 

13.98 

13.08 

11.76 

13.52 

14.26 

9.84 

4.25 

2.65 

2.13 

2.14 
2.72 
2.29 
1.57 

12991 

12412 

12475 

12571 

12220 

11691 

1202 

14814 

14716 

14604 

14472 

14403 

13890 

13867 

98 

210 

342 

411 

924 

947 

0.66 

1.42 

2.31 

2.77 

6.23 

6.39 



STORED 

UNDER 

WATER 




1031 

Same day. 

10.55 

4.25 

12891 

14814 

'98 


1081 

Same day as submerged 

13.98 

2.65 

12412 

14716 

0.66 

1647 

6 months. 

15.37 

3.34 

12013 

14524 

290 

1.96 

2100 

1 year. 

13.85 

3.81 

12231 

14517 

297 

2.00 

_ 1 - 


Note: For Unit Coal formula, see footnote to Table 12. 



























































16 


ILLINOIS ENGINEERING EXPERIMENT STATION 


Table 6 

Williamson County Nut Coal 


Sample Taken 

Dry Coal 

B. t. u. 
Referred 
to Actual 
or Unit 
Coal 

Decrease 

after jMining 

Ash 

Sulphur 

B. t. u. 

B. t. u. * 

Per Cent 


STORED IN EXPOSED BINS 


1090) 
1091 i 

Same day. 

13.98 

3.73 

12499 

14859 

— 


1098 

7 davs. 

14.90 

3.02 

12341 

14821 

38 

0.26 

1246 

2 months. 

14.32 

4.12 

12409 

14835 

24 

0.16 

1657 

6 months. 

13.81 

3.45 

12455 

14765 

95 

0.64 

2090 

1 year. 

11.88 

2.73 

12759 

14734 

125 

0.84 

4103 

3 years. 

12.52 

2.60 

12503 

14548 

311 

2.09 

7374 

6 years. 

12.86 

2.20 

12339 

14406 

453 

3.04 


STORED IN COVERED BINS 


1090 ) 

1091 1 
1098 
1247 
1663 
2096 
4100 
7299 

Same day. 

7 days. 

2 months. 

6 months. 

1 year. 

3 years. 

6 years. 

13.98 

14.90 

14.08 

13.06 

13.24 

13.93 

13.96 

3.73 

3.02 

3.84 

3.60 

3.20 

2.93 

2.16 

12499 

12341 

12378 

12469 

12428 

12085 

12103 

14859 

14821 

14739 

14644 

14616 

14323 

14324 

38 

120 

215 

243 

536 

535 

0.26 

0.81 

1.45 

1.64 

3.60 

3.60 


STORED 

UNDER 

WATER 




1090) 
1091 ) 

Same day. 

13.98 

3.73 

12499 

14859 



1098 

Same day as submerged 

14.90 

3.02 

12341 

14821 

38 

0.26 

1648 

6 months. 

15.65 

3.12 

12097 

14673 

186 

1.25 

2102 

1 year. 

14.87 

3.42 

12251 

14721 

138 

0.93 




























































Fig. 1. Open Storage Bins 



Fig. 2. Covered Storage Bins 
























EFFECTS OF STORAGE UPON THE PROPERTIES OP COAL 


19 


Table 7 

Sangamon County Nut Coal 


Lab. No. 

Sample Taken 

Dry Coal 

B. t. u. 

Referred 
to Actual 
or Unit 
Coal 

Decrease 

after Mining 

Ash 

Sulphur 

B. t. u. 

B. t. u. 

Per Cent 


STORED IN EXPOSED BINS 


1078 

Same day. 

17.87 

5.75 

11741 

14773 



1084 

7 days. 

16.63 

5.10 

11800 

14571 

202 

1.37 

1248 

2 months. 

17.45 

4.66 

11626 

14497 

276 

1.87 

1658 

6 months. 

16.03 

4.91 

11798 

14444 

329 

2.23 

2086 

1 year. 

14.97 

4.68 

11860 

14307 

466 

3.15 

4107 

3 years. 

15.55 

4.13 

11621 

14102 

671 

4.54 

7277 

6 years. 

14.10 

3.76 

11180 

13813 

960 

6.49 


STORED IN COVERED BINS 


1078 

Same day. 

17.87 

5.75 

11741 

14773 



1084 

7 days. 

16.63 

5.10 

11800 

14571 

202 

1.37 

1250A 

2 months. 

16.08 

5.03 

11912 

14600 

173 

1.17 

1250B 

2 months. 

17.57 

5.01 

11626 

14535 

238 

1.61 

1664 

6 months. 

16.30 

4.52 

11682 

14336 

437 

2.96 

2092 

1 year. 

15.99 

4.65 

11589 

14165 

608 

4.12 

4098 

3 years. 

17.34 

4.78 

10681 

13278 

1495 

10.11 

7370 

6 years. 

11.83 

1.45 

11971 

13767 

1006 

6.81 


STORED UNDER WATER 


1078 

Same day.. 

17.87 

5.75 

11741 

14773 



1084 

Same day as submerged 

16.63 

5.10 

11800 

14571 

202 

1.37 

1649 

6 months. 

15.90 

4.21 

11854 

14461 

322 

2.18 

2098 

1 year. 

15.95 

5.11 

11851 

14503 

270 

1.83 





























































20 


ILLINOIS ENGINEERING EXPERIMENT STATION 


Table 8 

'Vermilion County Screenings 


Sample Taken 

Dry Coal 

B. t. u. 

Referred 
to Actual 
or Unit 
Coal 

after Mining 

Ash 

Sulphur 

B. t. u. 


Lab. No. 


Decrease 


B. t. u. 


Per Cent 


STORED IN EXPOSED BINS 


1032 

Same day. 

17.88 

2.35 

11937 

14888 



1080 

7 days.. . 

13.98 

2.87 

12414 

14726 

162 

1.09 

1082 

7 days. 

13.69 

2.29 

12507 

14759 

129 

0.87 

1238 

2 months. 

15.73 

2.53 

11958 

14497 

391 

2.63 

1239 

2 months. 

14.69 

2.90 

12178 

14578 

310 

2.08 

1653 

6 months. 

15.63 

2.44 

11969 

14487 

401 

2.69 

2089 

1 year. 

14.46 

2.24 

12006 

14304 

584 

3.92 

4108 

3 years. 

15.95 

1.98 

11229 

13625 

1263 

8.48 

7369 

6 years. 

13.79 

3.85 

11210 

13275 

1613 

10.83 


STORED IN COVERED BINS 


1032 

1080 

1082 

1241 

1659 

2095 

4102 

Same day. 

7 days. 

7 days. 

2 months. 

6 months. 

1 year. 

3 years. 

17.88 

13.98 

13.69 

15.26 

14.51 

15.36 

14.43 

2.35 

2.87 

2.29 

2.51 

2.25 
2.42 

2.26 

11937 

12414 

12507 

12124 

12071 

11797 

11199 

14888 

14726 

14759 

14608 

14391 

14225 

13329 

162 

129 

280 

497 

663 

1559 

1.09 

0.87 

1.88 

3.34 

4.46 

10.47 


STORED 

UNDER 

WATER 




1032 

Same day. 

17.88 

2.35 

11937 

14888 



1080 

Same day as submerged 

13.98 

2.87 

12414 

14726 

162 

1.09 

1082 

Same day as submerged 

13.69 

2.29 

12507 

14759 

129 

1.87 

1644 

6 months. 

13.87 

2.32 

12270 

14514 

374 

2.51 

2101 

1 year. 

13.55 

2.71 

12283 

14483 

405 

2.72 




























































EFFECTS OF STORAGE UPON THE PROPERTIES OP COAL 


21 


Table 9 

Williamson County Screenings 


Sample Taken 

Dry Coal 

B. t. u. 
Referred 
to Actual 
or Unit 
Coal 

Decrease 

after Mining 

Ash 

Sulphur 

B. t. u. 

B. t. u. 

Per Cent 


Lab. No. 


STORED IN EXPOSED BINS 


1089 

Same day. 

14.13 

3.17 

12426 

14782 



1099 

7 days. 

14.37 

3.34 

12287 

14666 

116 

0.78 

1244 

2 months. 

15.66 

2.67 

12133 

14701 

81 

0.55 

1654 

6 months. 

13.76 

2.84 

12342 

14597 

185 

1.25 

2091 

1 year. 

13.77 

2.75 

12328 

14579 

203 

1.37 

4106 

3 years. 

13.25 

2.26 

13335 

14470 

312 

2.11 

7371 

6 years. 

13.42 

2.23 

12077 

14196 

586 

3.96 


STORED IN COVERED BINS 


1089 

Same day. 

14.13 

3.17 

12426 

14782 



1099 

7 days. 

14.37 

3.34 

12287 

14666 

116 

0.78 

1245 

2 months. 

12.62 

2.98 

12608 

14705 

77 

0.52 

1660 

6 months. 

13.60 

3.03 

12372 

14610 

172 

1.16 

2097 

1 year. 

13.43 

2.72 

12385 

14582 

200 

1.35 

4099 

3 years. 

13.07 

2.66 

12146 

14230 

552 

3.73 

7281 

6 years. 

12.64 

2.19 

12153 

14144 

638 

4.31 


STORED UNDER WATER 


1089 

Same day. 

14.13 

3.17 

12426 

14782 



1099 

Same day as submerged 

14.37 

3.34 

12287 

14666 

116 

0.78 

1645 

6 months. 

14.38 

3.54 

12262 

14645 

137 

0.93 

2103 

1 year. 

13.60 

2.97 

12447 

14698 

84 

0.57 


























































22 


ILLINOIS ENGINEERING EXPERIMENT STATION 


Table 10 

Sangamon County Screenings 


Lab. No. 


Sample Taken 

Dry Coal 

B. t. u. 
Referred 
to Actual 
or Unit 
Coal 

after Mining 

Ash 

Sulphur 

B. t. u. 


Decrease 


B. t. u. 


Per Cent 


STORED IN EXPOSED BINS 


1079 

Same day. 

17.13 

4.92 

11752 

14604 



1085 

7 days. 

17.04 

4.47 

11684 

14481 

123 

0.84 

1242 

2 months. 

17.22 

5.00 

11645 

14488 

116 

0.79 

1655 

6 months. 

17.02 

4.54 

11526 

14281 

323 

2.21 

2087 

1 year. 

17.25 

4.54 

11153 

13853 

751 

5.14 

4104 

3 years. 

15.94 

4.03 

11131 

13565 

1039 

7.11 

7373 

6 years. 

14.95 

3.32 

11326 

13604 

1000 

6.85 


STORED IN COVERED BINS 


1079 

Same day. 

17.13 

4.92 

11752 

14604 



1085 

7 days. 

17.04 

4.47 

11684 

14481 

123 

0.84 

1243 

2 months. 

18.33 

4.70 

11414 

14404 

200 

1.37 

1661 

6 months. 

17.30 

4.67 

11466 

14263 

341 

2.33 

2093 

1 year. 

17.06 

4.73 

11248 

13944 

660 

4.52 

4097 

3 years. 

18.71 

4.86 

10325 

13072 

1532 

10.48 

7279 

6 years. 

17.39 

3.81 

10497 

13025 

1579 

10.81 



STORED 

UNDER 

WATER 




1079 

Same day. 

17.13 

4.92 

11752 

14604 



1085 

Same day as submerged 

17.04 

4.47 

11684 

14481 

i23 

6.84 

1646 

6 months. 

19.86 

5.60 

11127 

14372 

232 

1.59 

2099 

1 year. 

18.27 

4.81 

11479 

14478 

126 

0.86 


6. Indicated Heat Losses .—An inspection of the tables shows 
that the heating value decreases most rapidly during the first week 
after mining and continues to decrease more and more slowly for 
an indefinite time. One per cent is about the average loss for the 
first week, and an additional loss of two or three per cent may occur 
by the end of the first year. At the end of the six-year period the 
indicated losses in some cases equal nearly eleven per cent. 

These losses may be ascribed to three distinct causes: 

(a) The escape of combustible gases. 

(b) The absorption of oxj^gen. 

(c) The increase in weight of the organic or combustible 

portion of the coal. 

























































EFFECTS OF STORAGE UPON THE PROPERTIES OF COAL 


23 


7. Escape of Coinhustihle Gases .—From certain experiments 
given in a former bulletin* there is positive evidence that combustible 
gases exude from freshly mined coal. The extent of this loss, how¬ 
ever, is very small. Porter and Ovitzf have carried out a quantitative 
measurement of such escaping gases and estimate in the case of a 
coal from Benton, Franklin County, Illinois, the total loss of heat 
values in a period of seventeen months to be 0.16 per cent. As this 
was an extreme case for this variety of coal it is evident that the heat 
loss due to the exudation of combustible gases is practically negligible. 

8. Ahsorption of Oxygen .—In Bulletin 32$ on the occluded 
gases in coal it is shown that freshly mined coal has a marked avidity 
for oxygen. It has been shown^j that the union of oxygen with the 
coal is a chemical combination and not a simple absorption. While 
we should expect such chemical action to be accompanied by the 
generation of heat and consequently by a reduction in the heat value 
of the coal, there is little information available as to the extent of 
such loss. 

Porter and Ralston§ show the positive formation of heat from 
oxygen combination but do not present any data as to the amount of 
this loss. Lamplaugh and Hill** have attempted to measure the 
amount of heat, and their results show an average for English coals 
of 3.3 calories for each cubic centimeter of oxygen absorbed. Winmill 
and Grahamft have carried the same line of experimentation further 
and have modified slightly the factor for the heat generated, their 
result showing 2.1 calories per cubic centimeter of oxygen absorbed. 
The difference is, for tlie purpose of the present discussion, not material 
since the desired re.sult is the approximate heat loss due to the oxygen 
combinations at ordinary temperatures. The maximum absorption 
under the most favorable circumstances ranges from 7 to 8 cc. oxygen 
per gram of coal as recorded in the experiments by Lamplaugh and 


*Parr and Wheeler, “The Deterioration of Coal Samples,’’ Univ, of Ill. Eng. Exp. 
Sta. Bui. 17, p. 33. 

tU. S. Bureau of Mines, Technical Paper No. 2, 1910. 

tPJ^i’i* and Barker, “The Occluded Gases in Coal,’’ Univ. of Ill. Eng. Exp. Sta. 
Bui. 32. 

UParr and Hadley, “The Analysis of Coal with Phenol as a Solvent,’’ Univ. of Ill. 
Eng. Exp. Sta. Bui. 76. 

§U. S. Bureau of Mines Tech. Paper 05, p. 8. 1914. 

**Trans. Inst. Mining Engrs., Vol. 45, p. 629, 1913. 

fi-Winmil] and Graham, “The Absorption of Oxygen by Coal,’’ Colliery Guardian, 
Sept. 11-18, 1915. 



24 


ILLINOIS ENGINEERING EXPERIMENT STATION 


Hill and also by Winmill and Graham. Porter and Ralston found in 
the case of a Franklin county, Illinois, coal exposed for five months 
at ordinary temperatures to pure oxygen, an absorption at the rate 
of 5.3 cc. per gram of coal. This is approximately 10 calories per 
kilo of coal or about 0.12 per cent of the heat value of the coal. The 
loss of heat thus represented is so small that it is negligible as a factor 
effecting deterioration in the quality of the coal. It may, however, 
possess significance in the matter of spontaneous heating. This 
phase of the subject will be hereinafter discussed. 

9. Increase in Weight .—It is evident that, if in the processes 
which attend the weathering of coal there is an increase in weight 
of the coal substance, the indicated heat losses are more apparent than 
real. For example, if at the beginning of the storage period a pound 
of the unit coal substance shows a value of 14,700 B.t.u., and at the 
end of the period the original pound has increased in weight by 
absorption or additions, say 5 per cent, then the heat value per pound 
of the resulting material will be 14,000 B.t.u., thus indicating an 
apparent loss of 4.76 per cent. Evidence from many sources has 
accumulated to show that coal exposed to air or oxygen increases in 
weight. In the experiments described by Parr and Hadley* it is 
shown that under certain conditions in the residue insoluble in phenol, 
which is regarded as the degradation product of the cellulose con¬ 
stituent, there is as much as 3 per cent increase in weight due to the 
taking up of oxygen. This work further shows that such additional 
oxygen is chemically combined and not merely absorbed. Other 
experimenters have presented evidence to the effect that coal increases 
in weight. Somermeierf has shown an increase due to oxidation for 
an Illinois coal 2.47 per cent. Porter and Ralston t show also a 
measurable increase in weight due to oxygen absorption. In their 
experiments on oxidation at various temperatures they note that Illi¬ 
nois and Pittsburgh coals ‘‘show increases of weight up to 260 degrees 
in spite of the loss of carbon and hydrogen in CO 2 , CO and HgO.’’ 
Study of some of the values presented in Table 11 seems to give 

*“The Analysis of Coal with Phenol as a Solvent,” Univ. of Ill. Eng. Exp. Sta. 
Bui. 76. 

tProfessor Somermeier was doubtless the first to suggest that the indicated decrease 
In heat values was in reality the result of an increase in weight. N. W. Lord and 
E. E. Somermeier, U. S. Geol. Surv. Bui. 323, p. 22. 

tU. S. Bureau of Mines, Tech. Paper 65, p. 20-22, 1914. 



EFFECTS OF STORAGE UPON THE PROPERTIES OF COAL 25 

further evidence of an increase in weight of the organic or combustible 
part of the coal. Some of these data with a discussion of their bearing 
on this point are presented under the following topic. 

10. Decrease of Ash Percentages .—A study of the relative ash 
values corresponding to the various stages of indicated heat losses 
reveals a consistent lowering of the percentages of ash. This result 
obviously is normal since the actual increase in the organic constitu¬ 
ents of coal during storage with the corresponding increase in the 
weight of any given sample must result in a relatively lower amount 
of ash, or an apparent decrease in ash. 

Of course, the exact duplication of these theoretical conditions 
was impossible in these experiments. The oxidation of the sulphur 
varied and the leaching out of the soluble sulphates would alter the 
ash values in a corresponding degree. Other variables might enter, 
such as irregularities in sampling or the possible accumulation of 
foreign or earthy matter. Notwithstanding all these possibilities of 
inaccuracy there is a striking consistency of results with reference 
to the decrease of indicated ash percentages as the process of weather¬ 
ing proceeded. The ash values of the several masses taken at the 
beginning and at the close of the six-year period are presented in 
Table 11. 


Table 11 

Indicated Ash at the Beginning and at the End of Six Years in Storage 

IN Open Bins 


No. 

Coal and County 

Average Ash Values 
as Determined by 
Analysis of 3 Samples 
(1) at the Mine 
(2) at Unloading of Car 
(3) after 2 Alonths 

Average Ash Values 
after 6 Years 
as Shown by 
Analysis of 2 Samples 
(1) from Open Bins 
(2) from Covered Bins 

Indicated 
Decrease 
in Ash 

1 

Nut—Sangamon. 

17.01 

12.96 

4.05 

2 

Nut—Vermilion. 

12.95 

11.45 

1.50 

3 

Nut—Williamson. 

14.32 

13.41 

0.91 

4 

Screenings—Sangamon.. 

17.43 

16.17 

1.26 

5 

Screenings—Vermilion .. 

15.20 

13.79 

1.41 

6 

Screenings—Williamson. 

14.19 

13.03 

1.16 


Inspection of the ash values presented in Tables 5 to 10, inclusive, 
further emphasizes the results shown by Table 11. The factors for 
the submerged coal have not been included in Table 11. Although 
















26 


ILLINOIS ENGINEEKING EXPERIMENT STATION 


these samples were under test for only a year, they show a con¬ 
stancy in the ash values and an absence of change, which is in keep¬ 
ing with the uniformity of heat values credited to the unit coal 
substance. 

The increase in weight of the coal in storage by addition to the 
organic constituents is further illustrated by the values presented 
in Table 12. The values jiPesented in Column 1 represent the heat 


Table 12 

Increases in Weight of Coal during Storage, in Relation to the Indicated 

Decrease in Heat Value 


No. 

Coal and County 

B. t. u. 
per Lb. of 
Fresh 
Coal 
Average 
of 3 

Samples 

Taken 

(1) at Mine 

(2) at Un¬ 
loading of 

Car 

(3) after 

2 Mos. 
Storage 

B. t. u. 
per Lb. 
after 6 
Years 
Open 
Storage, 
Dry 
Coal 
Basis 

Ash 

as 

Weighed 
Dry 
Coal 
Basis, 
with 
Heat 
Values 
as in 
Col. 2 

Sulphur 
in Dry 
Coal 
after 

6 Years 
Open 
Storage 

Ash 
Plus 
Addi- 
■ tive 
Mate¬ 
rial Ac¬ 
quired 
in 6 
Years 
Open 
Storage 

Ash 
as in 
Col. 3 
but 
Cor¬ 
rected 
for 

Sulphur 
as in 
For¬ 
mula 
for 
Unit 
Coal 

Show¬ 

ing 

Amount 

of 

Addi¬ 

tive 

Mate¬ 

rial 

by Dif¬ 
ference 



1 

2 

3 

4 

5 

6 

7 

1 

Nut— 









Sangamon. 

14,614 

11,180 

14.10 

3.76 

23.5 

17.3 

6.2 

2 

Nut— 









Vermilion. 

14,700 

11,984 

13.06 

1.58 

18.5 

14.9 

3.5 

3 

Nut— 









Williamson. 

14,838 

12,339 

12.86 

2.20 

16.9 

15.1 

1.8 

4 

Screenings— 









Sangamon. 

14,524 

11,326 

14.95 

3.32 

21.9 

17.9 

4.0 

5 ■ 

Screenings— 









Vermilion. 

14,717 

11,210 

13.79 

3.85 

23.8 

17.0 

5.2 

6 

Screenings— 









Williamson. 

14,716 

12,077 

13.42 

2.23 

17.2 

15.7 

1.5 


For discussion of Unit Coal and Corrected Ash see Univ. of Ill. Eng. Exp. Sta., Bui. 37, p. 33. 
U ‘t B t = (dry) B. t. u.—5000 sulphur 

1.00 — (1.08) +22/40 sulphur 

Corrected (dry) ash = ash as weighedXI.08+ 22/40 sulphur. 


value for the unit coal when fresh, as found by averaging the unit 
coal values for three samples taken at the mine, at the time of 
unloading, and after two months in storage. The calorific values of 
the dry coal in open storage at the end of six years are shown in 
Column 2. The accompanying ash and sulphur values are shown in 
Columns 3 and 4. Column 5 shows the percentages of ash or inert 
material which must be present in order that the fresh unit coal 























EFFECTS OF STORAGE UPON THE PROPERTIES OF COAL 


27 


values of Column 1 may after six years drop to the values shown in 3. 
These percentages are derived by the formula, 

B.t.u. per pound after storage 
B.t.u. per pound of fresh coal 

The values in Column 6 are the corrected ash values for the coal 
after six years in open storage.^' 

The difference between the apparent corrected ash values of 
Column 6 and the required ash for producing the values shown in 
Column 2 is a measure of the additive material which is assumed 
to have been taken up by the organic constituents as absorbed oxygen 
or hydroxyl additions. These additions bear a certain general rela¬ 
tion to the indicated decrease of ash shown in Table 11 and, of 
course, thus bear a more direct relation to the indicated deterioration 
percentages (see Tables 5 to 10). 

These facts taken together, therefore, seem to afford added basis 
for the statement that the actual losses of heat values in stored coal 
are apparent rather than real, and that the true heat losses are those 
due to escaping combustible gases and to the heat generated by direct 
combination of oxygen both of which have been shown to be prac¬ 
tically negligible. 


IV. Moisture Values for Weathered Coal 

The moisture values for the stored coal at the end of the six- 
year period are presented in Table 13. Some recent work on the 
Properties of the Water in Coalf by Porter and Ralston suggests a 
relation between the type of coal and the amount of ‘‘inherent” or 
hygroscopic moisture retained by the coal upon air-drying. It might 
be argued, therefore, that if the coals here considered during storage 
altered in type, possibly by a reversion toward the lignitic form, then 
a correspondingly high percentage of the moisture should be retained 
on air drying. The values shown in the table are without significance 
as far as this theory is concerned. However, the data should be 


♦Corrected Ash (dry) = ash X 1.08 -|-X sulphur (see formula for Unit Coal, 

footnote to Table 12). 40 

tH. C. Porter and O. C. Ralston, U. S. P.ureau of Mines, Technical Paper 113, 1916. 





28 


ILLINOIS ENGINEERING EXPERIMENT STATION 


presented for other reasons. For example, the high percentage of 
total moisture is in a general way characteristic of the several kinds 
of coal in that it is atfected by the degree of subdivision or disintegra¬ 
tion which has taken place. As may be seen by reference to the dis¬ 
cussion concerning the slacking of these coals, the coals which have 
undergone the greatest disintegration have the highest percentage of 
total moisture present. This result, however, is to be expected and 
is due to physical rather than to chemical action. 

V. Summary of Chemical Studies 

The results presented in the fdregoing tables and the data 
analyzed in the discussions may be summarized as follows: 

(1) After a period of one year, the indicated loss of heat 
values is relatively low, averaging about 3 or 3% per cent. 

(2) Ditferent coals vary in indicated heat losses, those 
from the southern Illinois districts showing less change than 
those from the central part of the state. Exposure beyond a 
period of one year accentuates this difference between coals 
from different localities. The denser coals, such as those from 
Williamson county, undergo but little additional change, while 
the coals from the northern parts of the state show a decrease 
in the indicated heat values. The difference, however, does not 
exceed about 10 per cent. 

(3) Deterioration is consistently greater in the case of 
screenings than in that of screened nut. 

(4) Since the heat values are referred to the unit coal 
basis, that is, the moisture, corrected ash, and sulphur free 
material, and since an actual loss of heat values by ordinary 
processes of oxidation would result in the formation of CO, 
and HsC, both volatile under the conditions, it follows that the 
heat losses are largely relative, since they must result from a 
relative increase in weight of the organic substance of the coal. 
For example, any increase in weight, as by the addition of 
oxygen to the chemical structure of the organic material, would 
result in a lower indicated heat value per pound of the unit 
substance as compared with the heat value per pound before 
such addition had occurred. Similarly, changes in the sulphur 
combination due to oxidation would increase the weight of the 


EFFECTS OF STORAGE UPON THE PROPERTIES OP COAL 


29 


coal in a manner not taken into consideration in deriving the 
“corrected’’ ash values. Thus, where FeSo becomes 2 FeS 04 
-f- THoO, the relative weights for sulphur are in the ratio of 
1:7; that is, the content of sulphur compounds as the result of 
the new combinations has increased in weight seven times. 

(5) Storage in open bins shows quite consistently a lower 
percentage of loss of heat value per pound than is the case with 
storage tmder cover. This is easily understood when it is con¬ 
sidered that the additional material formed, due to the oxidation 
of the sulphur, is soluble and tends to leach out under the long 
continued application of water resulting from exposure to the 
elements. For this reason, therefore, the increase in weight is 
greater in the case of the coal under cover than in that of the 
coal exposed in open bins. The resulting unit coal values should, 
therefore, be higher for the coal stored in open bins, or the 
leached coal, than for the coal stored under cover or the un¬ 
leached coal. Comparisons as to the relative values in covered 
and uncovered bins should, however, be made only up to and 
including the three-year period. The removal to new locations 
of the bins and piles shortly before the three-year old samples 
were taken resulted in the reconstruction of the covered bins 
with flat and leaky roofs through which the water had more 
or less free access to the coal. 

(6) The extent of oxidation or increase in weight is a 
function of the character of the coal. The coal in which the 
cellulose residuum seems to predominate has the greater avidity 
for oxygen, and the coal in which the resinic residuum predomi¬ 
nates is less affected. The tabulation of the samples, therefore, 
is in the order of such activity, namely, Sangamon, Vermilion, 
and Williamson counties. This feature is consistent with the 
studies in the absorptive capacities for oxygen of various coals 
as carried on by Porter and Ralston and is especially of interest 
in connection with the studies of Dr. Hadley on the relative 
avidity for oxygen of the cellulose residuum as compared with 
the’ absorptive capacity of the resinic bodies, separation into 
these two type components being affected by means of phenol.* 

*“The Analysis of Coal with Phenol as a Solvent,” Univ. of Ill. Eng. Exp. Sta. 

Bui. 76. p. 21, 1914. 



30 


ILLINOIS ENGINEERING EXPERIMENT STATION 


According to the results derived by Dr. Hadley, the cellulose 
residue had a far greater avidity for combination with oxygen 
than the resinic material. 


Table 13 

Percentage of Moisture in Weathered Coal, Loss Due to Air-Drying, and 
THE Amount Retained by the Air-Dried Samples 


Table 

No. 

Lab. 

No. 

Coal, County 
and Condition 

Total 

Moisture 

Loss 

Due to 
Air-Drying 

Moisture 
Retained 
in the 'j 
Air-Dried j . 
Sample j 

1 

7369 

Screenings 

Vermilion 

Exposed Bin 

17.70 

14.15 

4.14 

2 

7370 

Nut 

Sangamon 

Covered Bin 

19.95 

16.54 

4.09 

3 

7371 

Screenings 

Williamson 

Exposed Bin 

12.01 

8.59 

3.74 

4 

7372 

Nut 

Vermilion 

Covered Bin 

17.79 

14.50 

3.85 

5 

7373 

Screenings 

Sangamon 

Exposed Bin 

19.26 

15.79 

4.12 

6 

7374 

Nut 

Williamson 

Exposed Bin 

9.77 

7.05 

2.93 

7 

7277 

Nut 

Sangamon 

Exposed Bin 

20.35 

17.01 

4.03 

8 

7279 

Screenings 

Sangamon 

Covered Bin 

22.04 

19.36 

3.33 

9 

7298 

Nut 

Vermilion 

Covered Bin 

20.02 

16.01 

4.77 

10 

7299 

Nut^ 

Williamson 

Covered Bin 

12.54 

9.45 

3.30 


VI. Changes in Physical Properties 

11. Sizing Test .—The extent of the disintegration or ‘‘slacking” 
which takes place in connection with the storing of coal is a matter 
of considerable importance because of the effect upon combustion on 
the grates where a large amount of finely divided material is present 
In order to deteiunine the effect of storage upon slacking the sizing 
tests were continued to cover the entire period of six years. The 












EFFECTS OF STORAGE UPON THE PROPERTIES OF COAL 


31 


tests were made with a revolving screen with round perforations, as 
shown in Fig. 3. 

Three sizing tests were made: one at the time the coal was 
placed in storage, one after a period of eighteen months, and one at 
the end of six years. It should be recalled that approximately three 
years before the last screening tests the storage piles were removed 
by wagon to a new location involving a double handling. Since the 


Table 14 

Results of Sizing Tests on Nut Coal Stored in Open Bins 


Round-Hole 

Original 

In Storage 

In Storage 

Screen 

Sizes 

for 11^ Years 

for 6 Years 

Through 

Inches 

Over 

Inches 

Per Cent 

Cumulative 
Per Cent 

Per Cent 

Cumulative 
Per Cent 

Per Cent 

Cumulative 
Per Cent 


Sangamon County 


3 

1 

89.4 


64.3 


30.9 


1 


4.1 

93.5 

6.9 

71.2 

9.6 

40.5 

% 

y 

3.5 

97.0 

8.4 

79.6 

15.9 

56.4 

y2 

% 

1.2 

98.2 

3.2 

82.8 

8.5 

64.9 


y 

0.6 

98.8 

4.0 

86.8 

3.2 

68.1 

H 

y 

0.6 

99.4 

7.4 

94.2 

17.0 

85.1 


0 

0.6 

100.0 

5.8 

100.0 

14.9 

100.0 

Total. 


100.0 


100.0 


100.0 


Average Diameter ... 


1.854 inches 


1.442 inches 


.889 inches 


Vermilion County 


3 

1 

y 

y 

y 

1 

y 

y 

y 

y 

y 

0 

66.2 

5.0 

7.2 

4.0 

4.0 

5.0 

8.6 

71.2 

78.4 

82.4 

86.4 

91.4 
100.0 

42.5 

8.0 

11.8 

6.9 

6.8 

10.9 

13.1 

50.5 

62.3 

69.2 

76.0 

86.9 

100.0 

25.0 

6.3 

12.5 

8.7 

12.5 

16.3 

18.7 

31.3 

43.8 

52.5 

65.0 

81.3 

100.0 

Total. 

Average Diameter.... 

100.0 

1.458 inches 

100.0 

1.074 inches 

100.0 

.753 inches 


Williamson County 


3 

1 

94.0 


70.2 


60.6 


1 

Ya 

1.6 

95.6 

5.7 

75.9 

9.1 

69.7 

Ya. 

y^ 

1.8 

97.4 

6.6 

82.5 

8.3 

78.0 



0.7 

98.1 

3.1 

85.6 

2.7 

80.7 


y 

0.5 

98.6 

3.2 

88.8 

3.7 

84.4 


y 

0.5 

99.1 

4.6 

93.4 

5.5 

89.9 

y 

0 

0.9 

100.0 

6.6 

100.0 

10.1 

100.0 

Total. 


100.0 


100.0 


100.0 


Average Diameter ... 


1.910 inches 


1.532 inches 


1.383 inches 



















































32 ILLINOIS ENGINEERING EXPERIMENT STATION 

extent of disintegration was not materially different for the coals 
stored in the exposed bins and for those stored in the covered bins, 
and since during the last years of storage the covered bins were almost 
as much exposed to rain and weather conditions as the uncovered 
bins, the results of sizing tests on coals stored in covered bins are 
omitted. Those for the coals stored in open bins are presented in 
Tables 14 and 15. 


Table 15 

Results of Sizing Tests on Screenings in Open Bins 


Round-Hole 

Original 

In Storage 

In Storage 

Screen 

Sizes 

for 13^ Years 

for 6 Years 

Through 

Inches 

Over 

1 Inch 

Per Cent 

Cumulative 
Per Cent 

Per Cent 

Cumulative 
Per Cent 

Per Cent 

Cumulative 
Per Cent 


Sangamon County 


m 

1.0 

38.8 


15.1 


10.0 


1.0 

V 

7.9 

46.7 

9.3 

24.4 

8.2 

18.2 

H 

V 

13.2 

59.9 

15.6 

40.0 

14.5 

38.7 

H 

Vs 

6.6 

66.5 

7.7 

47.7 

10.9 

43.6 

Vs 


7.2 

73.7 

9.4 

57.1 

15.4 

59.0 

H 

Vs 

11.2 

84.9 

17.2 

74.3 

24.5 

83.5 

Vs 

0 

15.1 

100.0 

25.7 

100.0 

16.5 

100.0 

Total. 


100.0 


100.0 


100.0 


Average Diameter .. 


.768 inches 


.498 inches 


.452 inches 


Vermilion County 


IV 

1.0 

V 

v 

Vs 

V 

V 

1 

V 

V 

Vs 

V 

Vs 

0 

19.0 

8.9 

14.8 

8.5 

11.1 

16.4 

21.3 

27.9 

42.7 

51.2 

62.3 

78.7 
100.0 

11.3 

6.3 
12.9 

9.3 
11.8 
21.0 

27.4 

17.6 

30.5 

39.8 

51.6 

72.6 
100.0 

8.8 

6.3 
12.1 

9.3 
13.9 
29.0 
20.6 

15.1 

27.2 

36.5 

50.4 

79.4 

100.0 

Total. 

Average Diameter .. 

100.0 

. 548 inches 

100.0 

.425 inches 

100.0 

.403 inches 


Williamson County 


IV 

1.0 

V 

Vs 

V 

Vs 

1 

Vi 

Vs 

V 

Vs 

0 

18.9 

9.0 

14.4 

8.5 

10.4 

15.4 

23.4 

27.9 

42.3 

50.8 

61.2 

76.6 

100.0 

19.0 

9.2 

15.4 

9.5 

10.6 

17.0 

19.3 

28.2 

43.6 

53.1 

63.7 

80.7 
100.0 

6.0 

5.5 

11.5 

9.3 

14.4 

32.2 

21.1 

18.2 

32.7 

43.6 

59.0 

83.5 

100.0 

T otal. 

Average Diameter .. 

100.0 

.542 inches 

100.0 

.557 inches 

100.0 

.255 inches 



















































Fig. 3. Revolving Screens used in Sizing Tests 
(Reproduced from Univ. of Ill. Eng. Exp. Sta. Bui. 78, 1909) 











































) 




i_r’' ■■ 


\ 


% 

9 ^ 







> 




» • 





9 









EFFECTS OF STORAGE UPON THE PROPERTIES OF COAL 


35 


A condensed summary of the detailed results presented in Tables 
14 and 15 is given in Table 16. The total dust passing through a 
14 -inch screen is taken as the factor indicating the increase of fine 
material, and percentages of increase for the two periods are based 


Table 16 

Increase in Fine Material after One and One-Half and Six Years 
(Basis of Reference, the Total Coarse Material in the 
Original Coal Passing over 34-inch Screen) 





Initial 

Storage 

After IH Years 

After 6 Years 

Table 

No. 

Coal and County 

How 

Stored 

Dust 

Passing 

M-Inch 

Screen 

Dust 

Passing 

J^-Inch 

Screen 

Percentage 
Increase 
of Fine 
Material 
Referred to 
Original 
Coal over 
M-Inch 

Dust 

Passing 

J4-Inch 

Screen 

Percentage 
Increase 
of Fine 
Material 
Referred to 
Original 
Coal over 
^-^-Inch 

1 

Nut— 

Sangamon. 

Open 

1.2 

13.2 

12.1 • 

31.9 

31.0 

2 

Nut- 

Vermilion . 

Open 

13.6 

24.0 

12.0 

35.0 

24.7 

3 

Nut— 

Williamson.... 

Covered 

1.4 

11.0 

11.1 

13.9 

12.6 

4 

Screenings— 
Sangamon. .... 

Covered 

26.3 

38.5 

16.5 

45.1 

25.5 

5 

Screenings— 
Vermilion. 

Open 

37.7 

48.4 

17.1 

49.6 

19.1 

6 

Screenings— 
Williamson.... 

Covered 

38.8 

45.4 

10.7 

50.6 

19.2 


on the total amount of material in the original coal over 14 -ii^ch in 
size. Moreover, the samples taken from this table vary with reference 
to the method of storage, three being from exposed and three from 
covered bins. These particular samples are used in the table for the 
reason that the same storage lots were selected for making the stand¬ 
ard boiler tests which are hereinafter discussed. 

An examination of Table 16 shows that the rate of disintegra¬ 
tion is consistent with the variety of coal as already discussed in 
connection with the absorptive capacity for oxygen, and suggests that 
the process of oxidation of the organic material may be quite as 
largely responsible for this breaking down of the particles as the 
oxidation of the finely divided pyrite sulphur. The latter may or 
may not be distributed throughout the texture of the coal; this char¬ 
acteristic, for Illinois coal at least, has not been determined. 





















36 


ILLINOIS ENGINEERING EXPERIMENT STATION 


VII. Boiler Tests on Weathered Coal 

Upon the completion of the storage experiments at the end of 
the six-year period, it was decided to conduct if possible a series of 
boiler tests under standard conditions and to compare the results of 
tests with stored coal with those of similar tests in which fresh coal 
is used. Such an opportunity presented itself in connection with a 
series of boiler tests being conducted at that time by Mr. A. P. Kratz, 
who was making a general study of boiler losses.*' 

The coal which Mr. Kratz was using as standard material con¬ 
sisted of screenings from the Mission Field, Vermilion county, Illi¬ 
nois. Nineteen tests were conducted with this coal. Five additional 
tests were made on samples of the weathered coal, one sample each 
of nut coal being selected from the lots from Sangamon, Vermilion 
and Williamson counties, and one sample each of screenings from 
the Sangamon and the Williamson county lots. With reference to 
the ash content and the percentage of finely divided material, the 
properties of the stored coals did not differ greatly from those of the 
fresh coals. An excellent basis was, therefore, provided for comparing 
the efficiency of the stored and fresh coals. As might be expected, 
some experience had to be acquired as to the best method of handling 
and firing the weathered coals, and although the first test was unsatis¬ 
factory, subsequent experiments yielded results which proved trust¬ 
worthy and useful as a basis of comparison. 

‘ ‘ On the first test the coal banked slightly at the water-back, and 
the whole amount on the grate became clinkered. It immediately 
became evident that in order to run at all, the coal had to be kept 
away from the water-back. After the clinker had been removed 
a fresh start was made, and care was taken to keep the fuel bed from 
four to six inches away from the water-back. When this was done 
no further trouble was experienced.”! 

With reference to the relative drafts required for a given rate 
of combustion with the fresh and the weathered coal, the tests showed 
that a stronger draft is required for the weathered coal. Moreover, 
by comparing draft requirements for those lots which were in close 
agreement as to their dust content, it seems evident that the higher 
draft requirement is not necessarily due to a higher dust factor. The 


*A. P. Kratz, “Study of Boiler Losses,” Univ. of Ill. Eng. Exp. Sta. Bui. 78, 1915. 
tUnlv. of Ill. Eng. Exp. Sta. Bui. 78. p. 50, 1915. 



EFFECTS OF STORAGE UPON THE PROPERTIES OF COAL 


37 


explanation for this is simple if we recall the discnssion already pre¬ 
sented concerning the avidity for oxygen of freshly mined coal. 
This avidity for oxygen seems to he directly related to the free burn¬ 
ing character of the coal. Pillar coal and coal that has been long in 
storage does not burn so freely as fresh coal. On account of this 
characteristic such coal is thought to have lost a large part of its 
heat, when as a matter of fact it may have the same number of heat 
units but a very different rate of combustion. Another factor, and 
probably a minor one, is the loss of combustible gases. Mention has 
been made of the fact that part of the deterioration which occurs in 
the first few days or w’eeks after mining is due to the escape of 
certain light volatile or gaseous fuel constituents. It is evident, 
therefore, that either on account of the avidity of the fresh unsatu¬ 
rated coal for oxygen or the presence of light fuel constituent, or 
because of both conditions combined, the fresh unweathered coal 
burns freely and gives up its heat units readily, whereas the 
opposite is true with weathered coal. This difference, therefore, must 
be offset by a stronger draft or by some combination of conditions 
which will effect a speeding up of the burning or oxidation process. 
If by this means the rate of combustion can be made to approach 
that of the fresh coal, a corresponding degree of efficiency should 
result. The correctness of this theory is borne out by the results 
shown in Table 17. It is to be noted that the over-all efficiency of 


Table 17 

Results of Boiler Tests with Mission Field Fresh Coal and With 
Weathered Coal after Six Years in Storage 


Mission Field 

Weathered Coal 

Test 

No. 

Boiler H. P. 
Developed 

Efficiency 
of Boiler, 
Furnace, 
and Grate 
Per Cent 

Test 

No. 

No. 

Coal and County 
(Tables 5 to 10) 

Boiler H. P. 
Developed 

Efficiency 
of Boiler, 
Furnace, 
and Grate 
Per Cent 

10 

554.0 

63.96 

20 

1 

Nut— 








Sangamon. 

568.5 

64.50 

11 

569.6 

61.21 

21 

4 

Screenings— 








Sangamon. 

557.2 

63.05 

12 

572.7 

60.67 

22 

3 

Nut— 








Williamson. 

727.1 

65.98 

13 

589.0 

69.87 

23 

6 

Screenings— 








Williamson. 

509.6 

60.04 

14 

555.9 

64.75 

24 

2 

Nut— 








Vermilion. 

655.0 

64.20 

15 

506.6 

65.50 






16 

644.0 

60.84 






























38 


ILLINOIS ENGINEERING EXPERIMENT STATION 


the weathered coal averages quite as high as that of the fresh screen¬ 
ings. 

The general summary covering the behavior of the coal in steam 
generation after six years of storage, as set forth in Bulletin 78 of 
the University of Illinois Engineering Experiment Station, is as 
follows: 

“1. Burning weathered coal is largely a question of cor¬ 
rect handling and ignition. Under these circumstances it gives 
as good results as fresh screenings. 

‘'2. Weathered coal requires a little thinner fire and more 
draft than fresh screenings. 

‘‘3. When using weathered coal the fuel bed should not 
approach any nearer to the water-back than from 4 to 6 in., 
otherwise trouble with clinker is experienced. 

‘‘4. Practically as high capacity was obtained with weath¬ 
ered coal as with the other coals used, and, if anything, the fuel 
bed requires less attention.” 

In this reference, attention is called further to the fact that 
the results obtained and the conclusions presented are based on the 
heat values in the coal as fired and do not take into accoun{ the matter 
of deterioration. But it has already been shown in the previous dis¬ 
cussion that the deterioration is largely apparent in a physical change 
and that the actual loss of heat value is small. Hence, the efficiency 
factors developed in the tests may be accepted as fairly representing 
results obtainable on weathered coal in which the heat loss resulting 
from weathering is practically negligible. 

VIII. Conclusions 

The facts presented in the preceding sections of this bulletin 
jiLstify the following conclusions: ' 

(1) Bituminous coal can be stocked without appreciable 
loss of heat values provided the temperature is not allowed to 
rise above 180 degrees F. In fact, there is no appreciable evo¬ 
lution of COo at temperatures below 260 degrees F. 

(2) The indicated heat loss per pound of coal is due more 
largely to an increase in weight of a unit mass of coal resulting 
from the absorption of oxygen than to an actual deterioration 
or loss of heat units. 


EFFECTS OF STORAGE UPON THE PROPERTIES OF COAL 


39 


(3) Freshly mined coal has a large capacity for absorbing 
oxygen which combines chemically with both the organic com¬ 
bustible and the iron pyrites present. 

(4) The combination of oxygen with coal at ordinary tem¬ 
peratures generates a small increment of heat. 

(5) The rapidity with which oxygen is absorbed depends 
upon the temperature of the mass and the extent of the super¬ 
ficial area exposed, that is, the fineness of division of the coal. 

(6) If heat is generated by this slow process of oxidation 
more rapidly than it is lost by radiation, the acceleration of the 
reaction causes a rise in temperature which quickly brings the 
mass up to the danger point. A temperature of 180 degrees F. 
is named as the danger point because, if the coal reaches that 
temperature, practically all of the free moisture is vaporized 
and the further rise in temperature will be very rapid. 

(7) Any method of storage to be successful must either 
check or prevent the absorption of oxygen to such an extent that 
the generation of heat shall not proceed so rapidly as to exceed 
natural heat losses due to radiation. 

(8) Underwater storage prevents loss of heat values, and 
is not accompanied by deterioration in physical properties, such 
as slacking. 

(9) Dry storage is far more safely undertaken if the fine 
material is screened out at the storage yard and the lump only, 
preferably sized, is stocked. 






LIST OF 

PUBLICATIONS OF THE ENGINEERING EXPERIMENT STATION 


Bulletin No. 1. Tests of Reinforced Concrete Beams, by Arthur N. Talbot, 1904. None available. 

Circular No. 1. High-Speed Tool Steels, by L. P. Breckenridge. 1905. None available. 

_ Bulletin N^o. 2. Tests of High-Speed Tool Steels on Cast Iron, by L. P. Breckenridge and Henry 
B. Dirks. 1905. None available. 

Circular No. 2. Drainage of Earth Roads, by Ira O. Baker. 1906. None available. 

Circular No. 3. Fuel Tests with Illinois Coal (Compiled from tests made by the Technological 
Branch of the U. S. G. S., at the St. Louis, Mo., Fuel Testing Plan, 1904-1907), by L. P. Breckenridge 
and Paul Diserens. 1909. Thirty cents. 

Bulletin No. 3. The Engineering Experiment Station of the University of Illinois, by L. P. 
Breckenridge. 1906. None available. 

Bulletin No. 4. Tests of Reinforced Concrete Beams, Series of 1905, by Arthur N. Talbot 

1906. Forty-five cents. 

Bulletin No. 5. Resistance of Tubes to Collapse, by Albert P. Carman and M. L. Carr. 1906. 
None available. 

Bulletin No. 6. Holding Power of Railroad Spikes, by Roy I. Webber, 1906. None available. 

Bulletin No. 7. Fuel Tests with Illinois Coals, by L. P. Breckenridge, S. W. Parr, and Henry B. 
Dirks. 1906. None available. 

Bulletin No. 8. Tests of Concrete: I, Shear; II, Bond, by Arthur N. Talbot. 1906. None 
available. 

Bulletin No. 9. _An Extension of the Dewey Decimal System of Classification Applied to the 
Engineering Industries, by L. P. Breckenridge and G. A. Goodenough. 1906. Revised Edition 
1912. Fifty cents. 

Bulletin No. 10. Tests of Concrete and Reinforced Concrete Columns, Series of 1906, by 
Arthur N. Talbot. 1907. None available. 

Bulletin No. 11. The Effect of Scale on the Transmission of Heat through Locomotive Boiler 
Tubes, by Edward C. Schmidt and John M. Snodgrass. 1907. None available. 

Bulletin No. 12. Tests of Reinforced Concrete T-Beams, Series of 1906, by Arthur N. Talbot. 

1907. None available. 

Bulletin No. 13. An Extension of the Dewey Decimal System of Classification Applied to Archi¬ 
tecture and Building, by N. Clifford Ricker. 1907. None available. 

Bulletin No. II).. Tests of Reinforced Concrete Beams, Series of 1906, by Arthur N. Talbot. 

1907. None available. 

Bulletin No. 15. How to Burn Illinois Coal Without Smoke, by L. P. Breckenridge. 1908. 
None available. 

Bulletin No. 16. A Study of Roof Trusses, by N. Clifford Ricker. 1908. None available. 

Bulletin No. 17. The Weathering of Coal, by S. W. Parr, N. D. Hamilton, and W. F. Wheeler. 

1908. None available. 

Bulletin No. 18. The Strength of Chain Links, by G. A. Goodenough and L. E. Moore. 1908. 
Forty cents. 

Bulletin No. 19. Comparative Tests of Carbon, Metallized Carbon and Tantalum Filament 
Lamps, by T. H. Amrine. 1908. None available. 

Bulletin No. 20. Tests of Concrete and Reinforced Concrete Columns, Series of 1907, by Arthur 
N. Talbot. 1908. None available. 

Bulletin No. 21. Tests of a Liquid Air Plant, by C. S. Hudson and C. M. Garland. 1908. Fifteen 
cents. 

Bulletin No. 22. Tests of Cast-Iron and Reinforced Concrete Culvert Pipe, by Arthur N. Talbot. 
1908. None available. 

Bulletin No. 23. Voids, Settlement, and Weight of Crushed Stone, by Ira O. Baker. 1908 
Fifteen cents. 

*Bulletin No. 24. The Modification of Illinois Coal by Low Temperature Distillation, by S. W. Parr 
and C. K. Francis. 1908. Thirty cents. 

Bulletin No. 25. Lighting Country Homes by Private Electric Plants, by T. H. Amrine. 1908. 
Twenty cents. 

*A limited number of copies of bulletins starred is available for free distribution. 


41 



42 


PUBLICATIONS OF THE ENGINEERING EXPERIMENT STATION 


Bulletin No. 26. High Steam-Pressures in Locomotive Service. A Review of a Report to the 
Carnegie Institution of Washington, by W. F. M. Goss. 1908. Twenty-five cents. 

Bulletin No. 27. Tests of Brick Columns and Terra Cotta Block Columns, by Arthur N. Talbot 
and Duff A. Abrams. 1909. Twenty-five cents. 

Bulletin No. 28. A Test of Three Reinforced Concrete Beams, by Arthur N. Talbot. 1909. 
Fifteen cents. 

Bulletin No. 29. Tests of Reinforced Concrete Beams: Resistance to Web Stresses, Series of 
1907 and 1908, by Arthur N. Talbot. 1909. Forty-five cents. 

^Bulletin No. 30. On the Rate of Formation of Carbon Monoxide in Gas Producers, by J. K. Cle¬ 
ment, L. H. Adams, and C. N. Haskins. 1909. Twejity-five cents. 

*Bulletin No. 31. Fuel Tests with House-heating Boilers, by J. M. Snodgrass. 1909. Fifty-five 
cents. 

Bulletin No. 32. The Occluded Gases in Coal, by S. W. Parr and Perry Barker. 1909. Fifteen 
cents. 

Bulletin No. 33. Tests of Tungsten Lamps, by T. H. Amrine and A. Guell. 1909. Twenty cents. 

^Bulletin No. 34. Tests of Two Types of Tile-Roof Furnaces under a Water-Tube Boiler, by J. M. 
Snodgrass. 1909. Fifteen cents. 

Bulletin No. 35. A Study of Base and Bearing Plates for Columns and Beams, by N. Clifford 
Ricker. 1909. Twenty cents. 

Bulletin No. 36. The Thermal Conductivity of Fire-Clay at High Temperatures, by J. K. Clement 
and W. L. Egy. 1909. Twenty cents. 

Bulletin No. 37. Unit Coal and the Composition of Coal Ash, by S. W. Parr and W. F. Wheeler. 
1909. Thirty-five cents. 

*Bulletin No. 38. The Weathering of Coal, by S. W. Parr and W. F. Wheeler. 1909. Twenty- 
five cents. 

*Bulletin No. 39. Tests of Washed Grades of Illinois Coal, by C. S. McGovney. 1909. Seventy- 
five cents. 

Bulletin No. 40. A Study in Heat Transmission, by J. K. Clement and C. M. Garland. 1910. 
Ten cents. 

Bulletin No. 41- Tests of Timber Beams, by Arthur N. Talbot. 1910. Twenty cents. 

*Bulletin No. 4^- The Effect of Key ways on the Strength of Shafts, by Herbert F. Moore. 1910. 
Ten cents. 

Bulletin No. 43. Freight Train Resistance, by Edward C. Schmidt. 1910. Seventy-five cents. 

Bulletin No. 44- An Investigation of Built-up Columns Under Load, by Arthur N. Talbot and 
Herbert F. Moore. 1911. Thirty-five cents. 

*Bulletin No. 43. The Strength of Oxyacetylene Welds in Steel, by Herbert L. Whitemore. 1911. 
Thirty-five cents. 

^Bulletin No. 46. The Spontaneous Combustion of Coal, by S. W. Parr and F. W. Kressman. 
1911. Forty-five cents. 

*Bulletin No. 47. Magnetic Properties of Heusler Alloys, by Edward B. Stephenson, 1911. Twen¬ 
ty-five cents. 

*Bulletin No. 48. Resistance to Flow Through Locomotive Water Columns, by Arthur N. Talbot 
and Melvin L. Enger. 1911. Forty cents. 

*Bulletin No. 49. Tests of Nickel-Steel Riveted Joints, by Arthur N. Talbot and Herbert F. Moore. 
1911. Thirty cents. 

*Bulletin No. 50. Tests of a Suction Gas Producer, by C. M. Garland and A. P. Kratz. 1912. 
Fifty cents. 

Bulletin No. 51. Street Lighting, by J. M. Bryant and H. G. Hake. 1912. Thirty-five cents. 

*Bulletin No. 52. An Investigation of the Strength of Rolled Zinc, by Herbert F. Moore. 1912. 

Fifteen cents. 

^Bulletin No. 53. Inductance of Coils, by Morgan Brooks and H. M. Turner. 1912. Forti cents. 

*Bulletin No. 54- Mechanical Stresses in Transmission Lines, by A. Guell. 1912. Twenty cents. 

*Bulletin No. 55. Starting Currents of Transformers, with Special Reference to Transformers with 
Silicon Steel Cores, by Trygve D. Yensen. 1912. Twenty cents. 

*Bulletin No. 56. Tests of Columns: An Investigation of the Value of Concrete as Reinforcement 
for Structural Steel Columns, by Arthur N. Talbot and Arthur R. Lord. 1912. Twenty-five cents. 

*Bulletin No. 57. Superheated Steam in Locomotive Service. A Review of Publication No. 127 
of the Carnegie Institution of Washington, by W*. F. M. Goss. 1912. Forty cents. 


*A limited number of copies of bulletins starred is available for free distribution. 



PUBLICATIONS OF THE ENGINEERING EXPERIMENT STATION 


43 


*Bulletin No. 58. A New Analysis of the Cylinder Performance of Reciprocating Engines, by 
J. Paul Clayton. 1912. Sixty cents. & ^ , y 

^Bulletin No. 59. The Effect of Cold Weather Upon Train Resistance and Tonnage Rating, by 
Edward C. Schmidt and F. W. Marquis. 1912. Twenty cents. 

*Bulletin No. 60. The Coking of Coal at Low Temperatures, with a Preliminary Study of the 
By-Products, by S. W. Parr and H. L. Olin. 1912. Twenty-five cents, 

*Bulletin No. 61. Characteristics and Limitation of the Series Transformer, by A. R. Anderson 
and H. R. Woodrow. 1913. Twenty-five cents. 

Bulletin No. 62. The Electron Theory of Magnetism, by Elmer H. Williams. 1913. Thirty-five 
cents. 

Bulletin No. 63. Entropy-Temperature and Transmission Diagrams for Air, by C. R. Richards. 

1913. Twenty-five cents. 

*Bulletin No. 64. Tests of Reinforced Concrete Buildings Under Load, by Arthur N. Talbot and 
Willis A. Slater. 1913. Fifty cents. 

*Bulletin No. 65. The Steam Consumption of Locomotive Engines from the Indicator Diagrams, 
by J. Paul Clayton. 1913. Forty cents. 

Bulletin No. 66. The Properties of Saturated and Superheated Ammonia Vapor, by G. A. Good- 
enough and William Earl Mosher. 1913. Fifty cents. 

Bulletin No. 67. Reinforced Concrete Wall Footings and Column Footings, by Arthur N. Talbot. 

1913. Fifty cents. 

*Bulletin No. 68. Strength of I-Beams in Flexure, by Herbert F. Moore. 1913. Twenty cents. 

Bulletin No. 69. Coal Washing in Illinois, by F. C. Lincoln. 1913. Fifty cents. 

Bulletin No. 70. The Mortar-Making Qualities of Illinois Sands, by C. C. Wiley. 1913. Twenty 
cents. 

Bulletin No. 71. Tests of Bond between Concrete and Steel, by Duff A. Abrams. 1914. One 
dollar. 

*Bulletin No. 72. Magnetic and Other Properties of Electrolytic Iron Melted in Vacuo, by Trygve 
D. Yensen. 1914. Forty cents. 

Bulletin No. 73. Acoustics of Auditoriums, by F. R. Watson. 1914. Twenty cents. 

*Bulletin No. 74- The Tractive Resistance of a 28-Ton Electric Car, by Harold H. Dunn. 1914. 
Twenty-five cents. 

Bulletin No. 75. Thermal Properties of Steam, by G. A. Goodenough. 1914. Thirty-five cents. 

Bulletin No. 76. The Analysis of Coal with Phenol as a Solvent, by S. W. Parr and H. F. Hadley. 

1914. Twenty-five cents. 

*Bulletin No. 77. The Effect of Boron upon the Magnetic and Other Properties of Electrolytic 
Iron Melted in Vacuo, by Trygve D. Yensen. 1915. Ten cents. 

*Bulletin No. 78. A Study of Boiler Losses, by A. P. Kratz. 1915. Thirty-five cents. 

^Bulletin No. 79. The Coking of Coal at Low Temperatures, with Special Reference to the Prop¬ 
erties and Composition of the Products, by S. W. Parr and H. L. Olin. 1915. Twenty-five cents. 

^Bulletin No. 80. Wind Stresses in the Steel Frames of Office Buildings, by W. M. Wilson and 
G. A. Maney. 1915. Fifty cents. 

*Bulletin No. 81. Influence of Temperature on the Strength of Concrete, by A. B. McDaniel. 

1915. Fifteen cents. 

Bulletin No. 82. Laboratory Tests of a Consolidation Locomotive, by E. C. Schmidt, J. M. Snod¬ 
grass and R. B. Keller. 1915. Sixty-five cents. 

^Bulletin No. 83. Magnetic and Other Properties of Iron-Silicon Alloys. Melted in Vacuo, by 
Trygve D. Yensen. 1915. Thirty-five cents. 

Bulletin No. 84. Tests of Reinforced Concrete Flat Slab Structure, by A. N. Talbot and W. A. 
Slater. 1916. Sixty-five cents. 

*Bulletin No. 85. Strength and Stiffness of Steel Under Biaxial Loading, by A. T. Becker. 1916.. 
Thirty-five cents. 

*Bulletin No. 86. The Strength of I-Beams and Girders, by Herbert F. Moore and W. M. Wilson. 

1916. Thirty cents. 

*Bulletin No. 87. Correction of Echoes in the Auditorium, University of Illinois, by F. R. Watson 
and J. M. White. 1916. Fifteen cents. 

Bulletin No. 88. Dry Preparation of Bituminous Coal at Illinois Mines, by E. A. Holbrook. 1916. 
Seventy cents. 


*A limited number of copies of bulletins starred is available for free distribution. 




44 


PUBLICATIONS OF THE ENGINEERING EXPERIMENT STATION 


*Bulletin No, 89. Specific Gravity Studies of Illinois Coal, by Merle L. Nebel. 1916. Thirty 
cents. 

*Bulletin No. 90. Some Graphical Solutions of Electric Railway Problems by A. M. Buck. 1910. 
Twenty cents. 

^Bulletin No. 91. Subsidence Resulting from Mining, by L. E. Young and H. H. Stoek. 1916. 
One dollar. 

^Bulletin No. 92. The Tractive Resistance on Curves of a 28-Ton Electric Car, by E. C. Schmidt 
and H. H. Dunn. Twenty-five cents. 

^Bulletin No. 93. A Preliminary Study of the Alloys of Chromium, Copper, and Nickel, by D. F. 
McFarland and O. E. Harder. 1916. Thirty cents. 

^Bulletin No. 94- The Embrittling Action of Sodium Hydroxide on Soft Steel, by S. W. Parr. 
1917. Thirty cents. 

^Bulletin No. 95. Magnetic and Other Properties of Iron-Aluminum Alloys Melted in Vacuo, by 
Trygve D. Yensen and Walter A. Gatward. 1917. Twenty-five cents. 

*Bulletin No. 96. The Effect of Mouthpieces on the Flow of Water through a Submerged Short 
Pipe, by Fred B. Seely. 1917. Twenty-five cents. 

*Bulletin No. 97. Effects of Storage upon the Properties of Coal, by S. W. Parr. 1917. Twenty 
cents. 


* A limited number of copies of bulletins starred is available for free distribution. 



THE UNIVERSITY OF ILLINOIS 
THE STATE UNIVERSITY 
Urbana 

Edmund J. James, Ph. D., LL. D., President 


THE UNIVERSITY INCLUDES THE FOLLOWING DEPARTMENTS: 

The Graduate School 

The College of Liberal Arts and Sciences (Ancient and Modern Languages and 
Literatures; History, Economics, Political Science, Sociology; Philosophy, 
Psychology, Education; Mathematics; Astronomy; Geology; Physics; Chemistry; 
Botany, Zoology, Entomology; Physiology; Art and Design) 

The College of Commerce and Business Administration (General Business, Bank¬ 
ing, Insurance, Accountancy, Railway Administration, Foreign Commerce; 
Courses for Commercial Teachers and Commercial and Civic Secretaries) 

The College of Engineering (Architecture; Architectural, Ceramic, Civil, Electrical, 
Mechanical, Mining, Municipal and Sanitary, and Railway Engineering) 

The College of Agriculture (Agronomy; Animal Plusbandry; Dairy Husbandry; 
Horticulture and Landscape Gardening; Agricultural Extension; Teachers’ 
Course; Household Science) 

The College of Law (three years’ course) 

The School of Education 

The Course in Journalism 

The Courses in Chemistry and Chemical Engineering 
The School of Railway Engineering and Administration 
The School of Music (four years’ course) 

The School of Library Science (two years’ course) 

The College of Medicine (in Chicago) 

The College of Dentistry (in Chicago) 

The School of Pharmacy (in Chicago; Ph. G. and Ph. C. courses) 


The Summer Session (eight weeks) 

Experiment Stations and Scientific Bureaus: U. S. Agricultural Experiment 
Station; Engineering Experiment Station; State Laboratory of Natural His¬ 
tory; State Entomologist’s Office; Biological Experiment Station on Illinois 
River; State Water Survey; State Geological Survey; U. S. Bureau of Mines 
Experiment Station. 

The library collections contain (March 1, 1917) 387,442 volumes and 93,501 pam¬ 
phlets. 


For catalogs and information address 


THE REGISTRAR 
Urbana, Illinois 




